72 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 41-694-02 | ecoTEC exclusive 627 VU 256/5-7 (H-GB) | 2016–present |
| 41-694-02 | ecoTEC exclusive 627 VU 256/5-7 (H-GB) | 2016–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Tap any card for details
Your boiler has stopped working because it has lost the electronic signal from the sensor that monitors water temperature.
Your boiler has temporarily stopped working because a temperature sensor inside has lost its electrical connection.
Your boiler has detected a faulty connection or sensor on the hot water system, meaning it cannot properly monitor your hot water temperature.
Your boiler has temporarily lost connection to the hot water storage cylinder sensor, meaning it cannot properly monitor your hot water temperature.
Your boiler has detected a faulty temperature sensor or wiring issue, which has caused it to safely shut down to prevent overheating.
Your boiler has stopped working because it is getting an incorrect temperature reading from one of its internal sensors.
Your boiler has detected an electrical fault with the hot water temperature sensor, which means it cannot accurately measure how hot your water is getting.
Your boiler is temporarily unable to accurately measure the temperature of your hot water cylinder due to a faulty sensor or loose wiring.
Your boiler has safely shut down because it detected that the internal water temperature got too high.
Your boiler has temporarily stopped working because the water pressure inside the heating system has dropped too low.
Your boiler has temporarily stopped working because water is not flowing through it properly, which can cause the system to get dangerously hot.
Your boiler has shut down because the internal water temperature rose too quickly, usually caused by trapped air, low system pressure, or a circulation issue.
Your boiler has automatically shut down because the exhaust gases leaving the flue have become dangerously hot, or a safety sensor has been disconnected.
Your boiler has detected an issue with the valve that controls the gas supply, meaning it cannot safely ignite to provide heating or hot water.
Your boiler has detected moisture or a false flame signal inside the unit and has safely locked itself out to prevent unsafe operation.
Your boiler is failing to light because it cannot detect a successful flame or is not receiving enough gas to start up.
Your boiler has tried to start up several times but failed to ignite, usually because the gas supply has been temporarily interrupted or the system cannot clear exhaust gases properly.
Your boiler has detected an issue with the internal fan that safely removes combustion gases, causing it to lock out for safety.
Your boiler has temporarily stopped working because it has detected a blockage or issue with the airflow or flue system.
Your boiler has detected an issue with the airflow or the flue pipe that expels gases outside your home.
Your boiler has lost the digital signal from a key internal component, meaning it cannot safely recognise its own setup and has stopped working to protect itself.
Your boiler is having trouble communicating with its external controllers or thermostats, preventing it from receiving instructions to heat your home.
Your boiler has detected an issue with its internal carbon monoxide monitoring sensor, so it has safely shut down to protect you.
Your boiler has automatically shut down because it detected a dangerous level of combustion gases, which requires immediate attention from a qualified professional to ensure your safety.
Your boiler has temporarily stopped because it is running a specific sensor or calibration measuring test, which usually resolves itself or requires an engineer to complete the setup.
Your boiler has detected an issue with the internal gas valve control, meaning it cannot safely release gas to light the burner.
Your boiler has detected an issue with the gas valve shutting down properly, meaning it is safely locking itself out to prevent any potential safety hazards.
Your boiler's internal computer has encountered a memory error and cannot read the essential configuration data required to operate safely.
Your boiler has detected an internal electronic or sensor glitch and has safely shut down to prevent damage.
Your boiler has detected that the temperature of its internal electronic components is too high, so it has safely shut down to prevent permanent damage.
Your boiler has detected an internal communication problem with its electronic control system, meaning it cannot safely confirm the flame is burning correctly.
Your boiler is temporarily locking out because the flame inside is flickering or going out unexpectedly, meaning you currently have no heating or hot water.
Your boiler's computer memory has become corrupted, usually after a part has been replaced without being programmed correctly.
Your boiler is temporarily unable to accurately measure the temperature of the water flowing through the system, so it has safely shut down to prevent overheating.
Your boiler has detected a temperature mismatch between its internal water pipes, meaning it cannot safely regulate its heating.
Your boiler's water pressure sensor is sending an incorrect reading, meaning the system cannot accurately check how much water is inside.
Your boiler is temporarily unable to read its internal water pressure correctly due to a sensor issue.
Your boiler has detected a problem with the water pressure or the circulation pump, meaning it has safely shut down to prevent internal damage.
Your boiler has detected an issue with the way waste water or gases are leaving the system, causing it to lock out for safety.
Your boiler has detected a communication issue with a hot water sensor, which temporarily affects its ability to properly regulate the temperature of your hot water.
Your boiler is having trouble reading the temperature of the water coming into its hot water storage tank, which means your stored hot water may not heat up properly.
Your boiler is struggling to pump hot water to your cylinder, which means your stored hot water is not heating up properly.
Your boiler has detected an electrical fault with its internal corrosion-protection system, which means a qualified engineer needs to inspect the wiring.
Your boiler has detected an abnormal temperature difference between its sensors, meaning it cannot safely regulate the heat.
Your boiler has detected a confusing difference in temperature readings between its internal sensors, so it has safely shut down to prevent damage.
Your boiler has detected that its temperature sensors have been installed on the wrong pipes during recent maintenance or installation.
Your boiler's main computer is having trouble communicating with its internal parts, meaning it has temporarily stopped working for safety.
Your boiler has detected an issue with the internal water flow sensor and pressure system, meaning it has safely stopped working until the problem is checked.
Your boiler has noticed the temperature is very cold and has automatically turned itself on to prevent the internal pipes from freezing.
Your temperature settings are too low for the boiler to start heating, so the system is currently on standby.
Your boiler has temporarily stopped because it cannot get the internal fan spinning at the correct speed to safely clear exhaust gases.
Your boiler has temporarily shut down because an external safety device, such as a condensate pump or an overheat sensor, has told it to stop running to prevent damage.
Your boiler has temporarily reduced its heating performance to protect itself, meaning your radiators might not get as warm as usual while hot water continues to work normally.
Your boiler has too much water in the system, which is causing high pressure and has triggered a safety shutdown to protect the components.
Your boiler has temporarily stopped working because it has detected an issue with the exhaust flue's safety flap or the water drainage pump.
Your boiler is struggling to keep its flame steady while running at a very low power setting and has temporarily shut down to protect itself.
Your boiler has temporarily paused because the water is not flowing through the system fast enough, causing it to heat up too quickly.
Your boiler has temporarily paused itself because it detected that the water temperature is rising too quickly, suggesting there isn't enough water circulating through the system.
Your boiler is temporarily pausing its operation to allow its internal safety sensor to reset and calibrate.
Your boiler has temporarily paused its operation because it detected high carbon monoxide levels in the exhaust gases, and it is waiting to ensure it is safe to restart.
Your boiler is currently taking a short break to automatically re-calibrate its internal settings, during which it will temporarily pause heating and hot water production.
Your boiler has detected unusual airflow patterns, likely caused by strong winds outside, and has temporarily limited its heat output to keep the system stable and quiet.
Your boiler is temporarily pausing because it cannot detect enough water flowing through the system to heat it safely.
Your boiler has detected that the water level inside the heating system has dropped too low and needs to be topped up to function correctly.
Your boiler is displaying a routine reminder message to check the internal water flow sensor, but your heating and hot water should still be working normally.
Your boiler is currently running its automatic air-removal cycle, which is a normal process usually triggered after being refilled, serviced, or restarted.
Your boiler is running an automatic internal test to check the flow of water through the system.
Your boiler is temporarily pausing its operation to complete a required internal safety check of its exhaust gases.
Your boiler is performing a self-diagnostic check on its internal temperature sensors and has temporarily paused heating until it confirms everything is working correctly.
Your boiler is currently performing a self-test of its internal pressure sensor and has temporarily paused heating until it finishes.
Your boiler is temporarily running a self-test on its internal temperature sensors and pausing your heating until the check is finished.
Your boiler is currently running a routine internal check and will return to normal operation on its own shortly.
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.
BoilerFaultCodes